Almost every woodshop has some Hold Downs (or Holdfasts) because they are essential to secure the workpieces in place for safe operation. Hold Downs have been around for centuries, but most of them still need to be satisfactory. One of the flaws of the regular hold downs is that they are designed in deformable Cantilever Structures. When holding force is applied, the clamping point will produce excessive tilting displacement due to the bending deformation of the structure, which obviously will undermine the holding security and damage the workpiece surface. In addition, because of the overturning bending moment under loading, the hold down pillar shaft continuously damages the workbench dog holes. So it has been Harvey’s aspiration to design a better hold down for woodworkers.
Inspired by the ancient wisdom of Arch Building Structures, Harvey team came up with a completely new structural design for hold downs, called AH-3 Arch Hold Down. With the unique “Arch” shaped frame, the AH-3 is able to firmly hold workpiece down with no tilting deformation.
And it features a balancing leg which provides adaptive full balance to the working leg to eliminate any overturning moment on the pillar shaft. Also its innovative “Quick-Release Pressure Knob” and “Toolless Workbench Installation Mechanism” allow you to clamp your workpiece ideally with joy!
Besides the AH-3 Arch Hold Down, Harvey also created the AH-3T model – the version for T-slots mounting application.
By nature, an ideal Arch Structure is a pure compression mechanical form. When a vertical force is applied on its Crown Point (the highest point), the Arch will resolve the load into compressive stresses, and thereby eliminate tensile stresses. This miraculous property gives the structure a great deal of mechanical advantage over a beam structure (especially cantilever structure) , because the Arch can minimize the deformation.
Stress Analysis of the Arch
Stress Analysis of the Cantilever Structure
Owing to the unique Arch structure, the AH-3(T) hold downs are able to securely clamp the workpiece in place (with pure vertical pressure) without pressure deformation and overturning moment on the pillar shaft, thus achieving the highest stability.
Applicable for thick workpiece
Because of the balancing leg of the AH-3(T) and the mechanical nature of the Arch, clamping force on the working leg will be always automatically balanced without transferring any bending moment to the pillar shaft, no matter what the thickness of workpiece is.
Applicable for thin workpiece
The pressure applied by the Arch Hold Down can be easily adjusted to the proper amount by simply rotating the pressure knob. The maximum downward force applied by the Arch Hold Down can be as great as 1100N (246 lb) which is sufficient in most cases.
The pressure knob of the AH-3(T) hold downs is equipped with a Quick-Release Button to allow you quickly releasing the clamping force.
To eliminate the hassles of hold down installation on a workbench, Harvey developed a unique “Toolless Installation Mechanism” on the bottom of the Pillar Shaft. So when using the hold down, you simply insert the pillar shaft into a dog hole, the latch on the end of the shaft will automatically flip over (by off-center gravity) when it passe the bottom of bench top.
By turning the installation knob, you can easily lock the pillar shaft firmly between the upper and bottom surfaces of the bench top without touching the dog hole, and the pillar shaft is perfectly perpendicular to the bench top surface.
When removing the hold down, what you need is to unscrew the installation knob, the shaft latch will automatically retract (under gravity), and you can easily pull out the pillar shaft to remove the hold down. This smart and tricky mechanism makes the AH-3 a lot of fun to use!
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Customer Reviews
This is thoughtfully designed and perfectly engineered. My first task with this was to put an 80" x 23" piece of 3/4" oak ply through the table saw to trim the end square. Once I got the piece locked onto the sliding table it was immovably secured and the cut was made flawlessly and effortlessly.
Amazing build strong simply perfect 👌🏻
Amazing 100% recommended
These hold downs work very well - hold material with vigor. Added benefit - they are beautiful and extremely well thought out and engineered to accomplish their purpose.
Wonderful item very useful I like so much
I have had my eye on these since their initial release last year but the price has always held me back as I just couldn't see $160 for them. I was wanting one for the sliding table as this hold down seemed to be made with the table in mind but bought one for my work table as well.
Impressive! Well built, sturdy, precise with good parts fitment, and a little larger than I was expecting. You can tell that some thought went into the design. I know that it has one job, hold something down, but it does the job excellently. Not a toy as some others seem to be at times. Pleased with purchase and would buy again. Highly recommended.
Another precision product from Harvey. Every time I look at this equipment I am in awe. Truly amazing, beautiful and functional.
Excellent quality and easy to use hold down. Does its job well.